Conventionally, it has been necessary to use costly gas chromatography equipment, or the like, to analyze the compliments of a mixed gas when calculating the amount of heat production of a mixed gas. Additionally, there have been proposals for a method for calculating the amount of heat production from a mixed gas by calculating the ratio of methane (CH4), propane (C3H8), nitrogen (N2), and carbon dioxide gas (CO2) components included in the mixed gas through measuring the thermal conductivity of the mixed gas and the speed of sound in the mixed gas. (See, for example, Japanese Examined Patent Application Publication 2004-514138 (“JP '138”).)
However, the method disclosed in JP '138 requires a costly speed-of-sound sensor to measure the speed of sound, in addition to a sensor for measuring the thermal conductivity. Given this, an object of the present invention is the provision of a calorific value measuring system and calorific value measuring method whereby the calorific value of a gas can be measured easily.